<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        姓：<input type="text" v-model="firstName"> +
        名：<input type="text" v-model="lastName"> =
        <span>{{fullName}}</span><br><br> 
        <button @click="changeName">改名卡</button>
      </div>
      <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
      <script>
        const app = new Vue({
          el: '#app',
          data: {
             firstName: '刘',
             lastName: '备'
          },
          computed: {
            // !简写-> 获取，没有配置设置逻辑
            // fullName(){
            //     return this.firstName + this.lastName
            // }

            // ! 完整写法 -> 获取 + 设置
            fullName:{
                get() {
                    // #(1)当fullName计算属性，被获取求值时，执行get (有缓存，优先读)
                    // 会将返回值作为求值的结果
                    return this.firstName + this.lastName
                },
                    // #(2)当fullName计算属性被修改赋值时，执行set
                    // 修改的值，传递给set方法的形参
                set (value) {
                    // console.log(value.slice(0,1))
                    // console.log(value.slice(1)) 
                    this.firstName = value.slice(0,1)
                    this.lastName = value.slice(1)
                }
            }
          },
          methods: {
            changeName(){
                this.fullName = '吕小布'
            }
          }
        })
      </script>
</body>
</html>